This protocol hypothesizes that use of combination antiretroviral therapy will allow long-term control of viral replication with preservation of normal immune function when administered early in life to HIV-1 infected children. Specifically, this study will examine the antiretroviral activity of ZDV/3TC/NVP in vertically-infected infants and children aged 15 days to < 2 years, and ZDV/3TC/NVP/1592 in vertically-infected infants and children aged 30 days to < 2 years. The tempo of disease progression following vertical HIV-1 infection is highly variable. As a group, however, vertically-infected children experience more rapid disease progression than children infected at an older age or adults; over 80% of vertically-infected children manifest HIV-1 related symptoms or CD4 T cell depletion by 2 years of age. HIV-l's high replication rates appear to be responsible for the immune attrition and disease progression observed following HIV-1 infection. Studies in HIV-1 infected adults have generated estimates of an average HIV-1 generation time of 2.6 days (140 cycles/year) and an average daily production of 1010 virions per day; the average life span of a productively infected CD4 T cell has been estimated at 2.2 days. Similar studies allowing the calculation of these parameters have not been done to date in vertically-infected infants and children. Within this study, serial measurements of plasma HIV-1 virions and CD4 T cells on therapy will allow the calculation of viral and CD4 T cell kinetics in vertically-infected infants and children. These data, in turn, will likely prove useful in the design of future antiretroviral treatment strategies.